Gas recirculation systems



Dec. 19, 1967 Filed July 14,' 1964 FIGJ ) VALVE SOLENOID K. GOITEIN GAS RECIRCULATION SYSTEMS,

OXYGEN PRESSURE "REGULATOR 27 NEEDLE vALvE 2 VALVE 77 PRESSURE REGULATOR SOLENOID I PRESSURE REGULATOR PRESSURE REGULATOR SOLENOID vALvE 3 Sheets-Sheet 1 PRESSURE SWITCH TIME DELAY RELAY 82 T PILOT VALVE SWITCH F0 PUMP I2 cooLER PRESSURE REGULATOR PREssuRE REGULATOR 3 67 8 DRYER FILTER m HEATER CO ABSORBER R v RESTRICTO l COMPRESSION CHAMBER DRYER C O ABSORBER PRESSURE REGULATOR SOLENOID 44 47 vALvE.

CO2 ANALYZER CELL Dec. 19, 1967 K. GOlTElN 3,358,683

GAS RECIRCULATION SYSTEMS Filed July 14, 1964 3 Sheets-Sheet 3 United States Patent 3,358,683 GAS RECIRCULATION SYSTEMS Karl Goitein, Windsor, England, assignor to Vickers Limited, London, England, a British company Filed July 14, 1964, Ser. No. 382,477 Claims priority, application Great Britain, July 24, 1963, 29,404/ 63 8 Claims. (Ql. 128204) ABSTRACT OF THE DISCLOSURE Oxygen and air supply system with purification and re circulation features for a treatment chamber designed for receiving and enclosing a patient to be treated.

This invention relates to a gas recirculation system.

According to the present invention there is provided a gas recirculation system comprising a treatment chamber having a gas inlet and a gas outlet, at recirculation channel leading from the outlet to the inlet to form a circuit with the chamber, gas reconditioning means in said channel and an injector in said channel, the pump being adapted for connection to a source of gas under pressure, the arrangement being such that when the pump is supplied with gas from said source the pump circulates gas around said circuit and feeds the gas supplied by said source into the circuit.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

FIGURE 1 is a circuit diagram of an oxygen recirculation system for use in high pressure oxygen therapy,

FlGURE 2 is a diagrammatic cross-section of an injector pump used with the system of FIGURE 1,

FIGURES 3 and 4 are diagrammatic cross-sectional views of two nozzles which may be used in the injector pump of FIGURE 2,

FIGURE 5 is an axial section of a leak device used in the system of FIGURE 1, and

FIGURE 6 is an axial section of a lator used in the system of FIGURE 1.

The system shown in FIGURE 1 has an oxygen compression chamber 1 for receiving a patient to be treated, the oxygen being supplied to the chamber through an inlet pipe 2 and therebeing an outlet pipe 3 for the exhaust gases. Oxygen for the system is supplied from a source (not shown) to a supply line 4 through a shut-off valve 5, there being a supply pressure gauge 6 on the downstream side of the shut-01f valve 5. The supply line 4 then leads through a pressure regulator 7 having, on its downstream side, a gauge 8 for indicating the reduced pressure, followed by a pressure switch 9 for giving an alarm when the pressure falls below a predetermined value. After the switch 9, the supply line 4 is divided, one branch 10 leading through a two-way solenoid operated valve 11 and a pressure ratio regulator 60 to a jet pump 12. The regulator 60 is described in greater detail later. The valve 11 is arranged to be operated by contacts 1A associated with the door 1B of the chamber 1 so that it is open when the door is closed and closed when the the door is open. The jet pump 12 is in a closed circuit comprising the chamber 1, the inlet pipe 2 and the outlet pipe 3, the latter leading from the chamber 1 to the jet pump 12 through a carbon dioxide absorber 13 charged with soda lime granules and the outlet of the jet pump 12 being connected to the chambar 1 by the inlet pipe 2 which includes, in sequence from the jet pump 12, a cooler 14 which acts as a humidity or dew point control, a filter 15, a heater 16 and a pipe juncpressure ratio regution 17. The filter contains a material, such as activated alumina or charcoal, for removing organic vapours and odours. A switch 12A co-operates with the pump 12 to operate when the flow through the pump 12 falls below a predetermined value.

The other branch 18 of the supply line 4 downstream of the pressure switch 9 leads through a pressure regulator 19 to a three-way solenoid operated valve 20. The operation of the valve 20 is controlled by the door 1B of the chamber 1 which makes or breaks the contacts 1A upon opening or closing and there also being a time delay relay 82 in circuit with said contacts and the valve 26. The valve 20 has two outlet pipes, one being an outlet pipe 21 leading into a pipe 22 which adjoins the inlet pipe 2 at the junction 17. The other outlet pipe 23 of the valve 20 leads through a needle valve 24 and a flow regulator 25 into the pipe 22. A line 26 connects a point upstream of the needle valve 24 in the pipe 23 directly to the flow regulator 25 in such manner that the latter is made sensitive to the pressure drop across the valve 24 to maintain an even flow of oxygen in the pipe 23 when the latter is opened to the supply through the valve 20. A further needle valve 27 is mechanically interlocked with the valve 24 and is disposed at the end of a decompression line 28 leading from the outlet pipe 3 from a point upstream of the carbon dioxide absorber 13. A pressure regulator 29 is disposed in the line 28 upstream of the valve 27 and is set to give a constant low output pressure, for example three pounds per square inch. The valves 24 and 27 are interlocked to give three conditions, a first condition in which the pipe 23 and the line 28 are blocked, a second condition in which the pipe 23 is open and the line 28 blocked and a third condition in which the pipe 23 is blocked and the line 28 is open to exhaust. Conveniently the valves 24 and 27 are operated by a knob 27A interlocked with the valves and a pointer co-operating with a scale (not shown). The scale has a 12 oclock inscription Hold signifying the first condition and clockwise and anticlockwise arrows marked Pressurise and Decompress respectively. The scale also has calibration lines to show the rate set for compression or decompression. v The decompression line 23 has a branch 39 leading from it to exhaust through a pilot operated relief valve 31, and a pilot pressure line 61 connects the line 28 to the pressure ratio regulator '60. Downstream of the branch 30, the line 28 has a leak device 32. The control for the pilot operated relief valve 31 is by means of oxygen taken from the supply line 4- from a point downstream of the pressure switch 9, this control line 33 leading through a pressure regulator 34 by which the maximum chamber pressure can be set, a'three-way solenoid valve 35 and a three-way pilot valve 36 to the pilot operated relief valve 31. The valve 35 is arranged to be operated by the door of the chamber 1 in the manner of the valve 20 so that it opens the part of the line 33 leading from the valve 36 to exhaust when the door is closed, and the time delay relay 32 which is also associated with the valve 20 changes over the valve 35 a predetermined time after that closure. A maximum chamber pressure gauge 37 is connected to the line 33 between the regulator 34 and the valve 35. The pilot operated relief valve 31 is a diaphragm operated large bore valve, the diaphragm normally being loaded by the pilot pressure in such a way that the valve is closed as long as the closed circuit pressure is below the pilot pressure, but so that it opens the closed circuit to atmosphere when the closed circuit pressure is greater than the pilot pressure. The valve 36 is push button operated for connecting the part of the line 33 leading to the valve 31 to atmosphere.

A carbon dioxide analysing device is connected between a point in the inlet pipe 2 between the cooler 14 and the charcoal filter 15 and the part of the outlet pipe 3 upstream of the carbon dioxide absorber 13. This carbon dioxide analysing device has a line 33 leading from said point in the pipe 2 through a pressure regulator 39, a carbon dioxide absorber 40, in the form of a tubular soda lime container, and a dryer 41 to a capillary restrictor 42 which leads to one side of a carbon dioxide analysing cell 43. A line 44 leads from the pipe 3 through a pressure regulator 45 and a dryer 46 to a three-way solenoid operated valve 47. The line 44 can be connected through the valve 47 and via a capillary restrictor 48 to the other side of the carbon dioxide analysing cell 43. The valve 47 is operable to open the line 38 to both sides of the cell 43 while blocking the line 44. A warning device (not shown) and an indicating instrument (not shown) are connected to the cell 43 so that the amount of CO in the exhaust gases is shown by the indicating instrument and an alarm is given when the CO content reaches a dangerous level. This cell 43 Works on the principle of measuring purity in which the conductivity of a sample of the gas to be analysed is compared with that of a standard gas, in this case carbon dioxide free gas from the closed circuit.

A pressure gauge 49 is provided for indicating the pressure in the chamber 1 and a thermometer (not shown) and a humidistat (not shown) may also be provided on the chamber 1. A thermostat (not shown) within the chamber 1 is connected to control the heater 16 and the cooler 14 may also be controlled by a thermostat (not shown).

The jet pump 12 is shown in greater detail in FIGURE 2. The oxygen from the solenoid valve 11 is supplied to a nozzle 50 and the recirculated gas from the pipe 3 to an inlet 51, the mouths of the nozzle 50 and the inlet 51 being concentrically arranged at the entrance of a venturi tube 52. Two difierent forms of nozzle 50 are illustrated in FIGURES 3 and 4, FIGURE 3 showing a shape suitable for sub-sonic oxygen jet speeds and FIGURE -4 showing the shape of a nozzle by which super-sonic oxygen jet speeds may be achieved. The jet of oxygen issuing from the nozzle 50 drives the gas in the closed circuit around the closed circuit and through the reconditioning elements 13 to 16 in addition to supplying the oxygen needed to make up for that used by the patient and that lost through leakages.

The leak device 32 may simply be a constant area orifice. A more refined device, however, that may be employed is shown in FIGURE 5. This device has a cylinder 53 in which a piston 54 having a central orifice 55 is urged by a spring 56 towards the lower end of the cylinder which is in communication via a connector '57 with the decompression line 28. A fixed needle 58 co-operates with orifice S progressively to close the latter when the piston 54 moves away from the connector 57 against the action of the spring 56. A hole 59 in the cylinder 53 opens the space above the piston 54 to atmosphere. The position of the piston 54 is determined by the equilibrium between the pressure in the chamber 1 acting on the underside area of the piston and the force of the spring 56, and the fixed needle 58 is so shaped that a constant mass leak results at all chamber pressures within a certain range.

One form of the pressure regulator 66 is shown in FIGURE 6. The regulator has two diaphragms 62 and 63 Whose centres are mechanically coupled by a spacing element 64 and whose perimeters are clamped to opposite end faces of a ring 65. The chamber formed between the diaphragms 62 and 63 is open to atmosphere through a bore 66 in the ring 65. A cap 67 covers the side of the diaphragm 62 remote from the ring 65 to form a chamber 68 into which the pilot pressure line 61 leads so that gas at chamber pressure acts on the upper face (FIG. 6) of the diaphragm 62. A spring 69 in the chamber 68 acts on the diaphragm 62 to supply a downward force on the diaphragm 62 additive to the pneumatic force caused by gas at super-atmospheric pressure in the chamber 68. A valve housing 70 covers the underside of the diaphragm 63 and has an inlet 71 for oxygen supplied from the valve 11, and an outlet 72 for connection to the continuation of the branch 10 which leads to the jet pump 12. An inclined duct 73 leads from a chamber 74, one of whose walls is the underside of the diaphragm 63, to the outlet 72 so that oxygen at outlet pressure acts on the underside of the diaphragm 63.

Centrally mounted within the housing 70 is a mushroom shaped valve member 75 biased upwardly by a spring 76 against a seat formed by the bottom end of a hollow cylindrical portion '77 of the housing 76. The upper end of the portion 77 opens into the chamber 74 and an extension 7 8 of the valve member 75 is disposed co-axially of the portion 77. A ball end 79 of the extension 78 is received in a central recess of a circular plate 80 between which and the spacing element is clamped the centre of the diaphragm 63. The ball end 79 covers a hole in the plate -33 which is the entrance to ducts 81 through the spacing element 64 which serve, when the ball end 79 is unseated firom the recess, as a leakage passage for oxygen in the chamber 74 to atmosphere. When the valve member 75 is unseated from the cylindrical portion 77, a passage for oxygen lies from the inlet 71 to the outlet 72 via the interior of the portion 77, the chamber '74 and the duct 73.

In operation of the regulator 60, gas at chamber pressure P fills the chamber 68 and acts on the effective area A of the diaphragm 62. Oxygen at a pressure P; pushes upwardly on the eiiective area A; of the diaphragm 63, P being the pressure of oxygen in the outlet 72, i.e. the pressure of the oxygen fed. to the jet pump 12 when the valve 11 is open. The resultant downward force on the diaphragm 63 acts through the ball end 79 and the extension 78 ordinarily to maintain the valve member 75 unseated from the portion 77 and allows oxygen to pass from the inlet 71 to the outlet 72. In this equilibrium state, assuming the resultant downward force of the springs 69 and 76 to be K and the atmospheric pressure to be P o( o a)+ l( 1 a) which may be transformed to:

A K A P==- P PB a By choosing A P =P The pressure P of oxygen supplied from the outlet 72 of the regulator 64} is therefore directly proportional to the chamber pressure P In all the above equations the pressures P P and P are absolute. It should be noted that initially, with the pressure in the chamber 68 atmospheric, the spring 69 is sufficiently strong to hold the valve in the housing 70 just open to allow oxygen to pass from the inlet 71 to the outlet 72.

When any pressure increase in the chamber 1 occurs the valve member 75 is moved so that an increased amount of oxygen is supplied to the jet pump 12 and vice versa. If the chamber pressure falls to such a level that the valve member 75 seats against the portion 77 and the oxygen pressure in the chamber 74 lifts the diaphragm 63 so that the ball end 79 is unseated from the recess of the plate 80, oxygen escapes from the outlet 72 to atmosphere via the bore 66. This pressure ratio regulator 60 may be dispensed with it" pressures in the circuit of up to only 15 p.s.i.g. above atmospheric are contemplated. The regulator 60 promotes constant volume flow in the circuit and, at higher pressures, keeps the partial pressure of CO low.

The flow switch 12A is a device which makes (or breaks) a contact if the diiferential pressure between the outlet and the throat of the jet pump venturi, i.e., the

flow, drops below a predetermined value which is the safe minimum for the closed circuit. The contact can be used to operate an audible alarm (not shown) and, by means of a relay (not shown), to switch off the cooler 14 and the heater 16.

The operation of the system is as follows. The shut-off valve 5 is opened and oxygen passes through the regulator 7 to the branches 10 and 18 with the valves 24 and 27 set to said first condition. The door of the chamber 1 is then closed on the patient so that the valve 20 is actuated to assume the condition in which the pipe 23 is blocked and oxygen passes from the branch 18 to the pipe 21, by-passing the valve 24 and the flow regulator 25. This closing also operates the valve 11 to pass oxygen to the jet pump 12 and the valve 35 to open the outlet pipe 3 to exhaust via the line 28, the branch 30, and the relief valve 31. Under these conditions oxygen in relatively large quantities is introduced into the chamber 1, flushing out the air that was in the chamber 1 through the valve 31. During this flushing out period, the maximum pressure to which the chamber 1 is to be raised during the treatment is set by means of the regulator 34 which admits oxygen from the line 4 to the gauge 37 at this desired maximum pressure. The regulator 34 is set in this position so that the gauge 37 continues to register this maximum pressure throughout the operation of the system.

After a predetermined time interval from the closing of the door of the chamber 1, the time delay relay 82 operates the change over of valve 35 so that the maximum set pressure is passed along the line 33 through the valve 36 to the pilot operated relief valve 31, which cuts off the escape of flushed air to exhaust upon loading of its diaphragm by the pilot pressure from the line 33, since at this time the pressure in the line 33 is greater than that in the branch 30. The time delay relay simultaneously causes the valve 20 to change over so that it blocks the pipe 21 and admits oxygen to the Valve 24 which is open. The closed circuit is now established and pressure in the chamber 1 starts to build up, oxygen being supplied to the chamber 1 both from the jet pump 12 and from the pipe 22, the flow in the latter being regulated by the regulator 25. The pilot pressure at the valve 31, which is the maximum set pressure, maintains the valve 31 closed until the pressure in the closed circuit exceeds this maximum set pressure, but the leak device 32 allows a certain amount of oxygen to escape from the closed circuit to compensate for the introduction into the closed circuit of oxygen through the jet pump 12 which is not regulated and which can cause too rapid a rate of build up of pressure in the chamber 1. The needle of the valve 24 can be adjusted to increase or decrease the pressurisation rate.

When the desired pressure in the chamber 1 has been reached the valve 24 is operated completely to block the branch 18, but oxygen continues to be fed into the closed circuit via the jet pump 12. Part of the exhaust gases from the chamber 1 continues to leak through the device 32, but the remainder passes through the CO absorber 13 and thence to the jet pump 12. The combined oxygen and purified return gases are forced by the pump 12 through the cooler 14 which condenses a proportion of the moisture in the gas, through the filter 15 and then through the heater 16 which restores the gas to a temperature suitable for the patient in the chamber 1, The carbon dioxide analysing device is set up after pressurisation by operating the valve 47 so that both sides of the cell 43 are supplied with oxygen from the line 38. The cell 43 is adjusted so that a zero reading is given on the CO indicating instrument. The valve 47 is then changed over so that one side of the cell 43 is connected to the inlet pipe 2 and the other side to the outlet pipe 3. The CO absorber 40 in' the line 38 removes all residual traces of carbon dioxide that may remain even after the absorber 13 and this extra purified gas is used as the standard with which the exhaust gases are compared. By taking the standard gas from the closed circuit and not direct from the oxygen supply any nitrogen that is in the closed circuit acts on both sides of the analysing cell 43, avoiding the errors which could arise if pure oxygen was supplied to one side of the cell and gas containing nitrogen was supplied to the other. During steady operation of the system, the pressure regulator 7 ensures the supply of oxygen at constant pressure to the jet pump 12 and there is substantially constant volume recirculation flow if a sonic jet nozzle is employed with the jet pump 12 and the pilot operated relief valve remains closed. Should the pressure increase above the maximum set value, the pressure in the closed circuit opens the relief valve 31 and gas escapes from the circuit until the pressure drops below the maximum set value. The pilot operated relief valve 31 can also be operated by manually pressing the push button of the pilot valve 36 Which changes over so that the part of the line 33 leading from the valve 35 is blocked and the part of the line between the valve 36 and the valve 31 is open to exhaust. The pressure in the branch 30 will then open the valve 31 and gas can escape from the closed circuit through that valve.

When the treatment of the patient is completed the pressure in the chamber 1 is reduced by adjusting the valve 27 so that gas can escape from the closed circuit via the decompression line 28 through the valve. By the interlocking arrangement between the valve 27 and the valve 24, the valve 24 remains closed. The rate of decompression can be adjusted by suitable manipulation of the needle of the valve 27. When the pressure in the chamber 1 approaches that of atmosphere the escape of gas through the needle valve 27 will decrease, owing to the decreasing pressure differential across that valve, thus slowing the decompression process. In order to avoid undue delay the push button of the pilot valve 36 can be pressed allowing quicker escape of gas from the chamber 1 via the valve 31. When the pressure in the chamber 1 is the same as that of atmosphere, the door of the chamber 1 is opened, closing the solenoid operated valve 11, and the patient can be removed from the chamber. If necessary, the charge in the CO absorber 13 can be changed.

If for example there is an electrical fault, e.g. mains failure, or the cooler 14 or the heater 16 fail to work, the system can be used as an open circuit by opening the valve 24 fully so that a sufiicient quantity of fresh oxygen is supplied to the chamber 1 via the pipe 22. Any build-up of pressure is prevented by the operation of the relief valve 31.

In a variant (not shown) of the reconditioning elements shown, a silica gel absorber may be provided for humidity control and the cooler 14 used for temperature control alone. The heater 16 can be dispensed with in such an arrangement since CO absorption and water vapour absorption together with the heat output of the patient raise the temperature of the gas flowing from the chamber 1 to above the required temperature. The circuit described above has some of the reconditioning elements connected between the output of the jet pump 12 and the chamber 1. In a variant (not shown) these three conditioning elements may be inserted in the outlet pipe 3 with the result that the output of the jet pump 12 is fed directly to the junction 17. In another variant (not shown) the CO absorber 13 is placed downstream of the jet pump 12.

It will be understood that the solenoid valves of the system described may be replaced by manual or pilot pressure operated valves, the electrically operated cooler 14 by non-electrical devices such as air or water coolers, or gas expansion coolers and the electrically operated heater 16 by a heater using gas or liquid fuel.

I claim:

1. Apparatus for super-atmospheric oxygen therapy comprising:

(a) a treatment be treated,

(b) a door for said chamber for sealing the latter with the patient therein,

.(c) a source of high pressure oxygen,

(d) an inlet to said chamber,

(e) an outlet from said chamber,

(f) a conduit connecting said source to said inlet,

(g) means for controlling increase of pressure in said I chamber from atmospheric up to the desired treatment pressure,

(h) means for preventing said treatment pressure exceeding a set value,

(i) means for controlling decrease of pressure in said chamber from the treatment pressure down to atmospheric,

(j) a recirculation channel leading from said outlet to said inlet to form a substantially closed circuit with said chamber and having a junction with said conduit,

(k) gas reconditioning means in said channel,

(1) an injector pump at said junction for circulating gas around said circuit and for introducing oxygen from said source into said circuit, and

i (in) means for maintaining a constant ratio between the absolute pressure of oxygen supplied to the injector pump from said source and the absolute pressure of gas in said chamber.

2. Apparatus according to claim 1, wherein the means for controlling increase and decrease of pressure in said chamber include a further conduit between said source and said inlet, bypassing said pump, first valve means in said further conduit, a decompression conduit from said outlet, second valve means in said decompression conduit, and means interlocking said first and second valve means to permit one or the other to open or both to be closed.

3. Apparatus according to claim 2, wherein a changeover valve is disposed in said further conduit upstream of said first valve means and another conduit leads from said changeover valve to a point in said further conduit downstream of said first valve means.

4. Apparatus according to claim 3, wherein means actuated by said door control said changeover valve to open said further conduit when the door is closed and to close said further conduit a predetermined time after such closure.

5. Apparatus according to claim 4, wherein the means for preventing the treatment pressure exceeding a set value include a conduit leading from said outlet, a valve chamber for receiving the patient to in this conduit, a pilot pressure line from said source to said valve and a pressure regulator in said pilot pressure line for setting said treatment pressure downstream thereof, said valve including means balancing the set treatment pressure against the chamber pressure to maintain the valve closed unless the chamber pressure exceeds the set treatment pressure.

6. Apparatus according to claim 5, wherein said pilot pressure line includes a valve for opening that line to exhaust downstream of the pressure regulator, and the door actuated means also control this valve to maintain it in the condition opening said line to exhaust during the predetermined time after closure.

7. Apparatus according to claim 1, and further comprising a leak device for permitting a continuous constant mass leak of gas from said circuit at all chamber pressure Within a predetermined range, the leak device including an apertured means and. means closing the aperture through which said leak takes place in response to an increase in chamber pressure.

8. Apparatus according to claim 1, and further comprising a carbon dioxide analysing device for indicating the carbon dioxide content of the exhaust gases from the chamber, the device including a cell that works on the principle of measuring purity by comparing the conductivity of a standard gas with a sample gas, the cell having two parts, a first conduit connecting one part to a point in said circuit between the pump and the inlet, a second conduit for placing the other part of the cell in communication with said outlet, nad a changeover valve connecting said cell with said conduits for alternatively connecting both parts of said cell to said first conduit for zeroing the device or for connecting the parts of the cell one to said first conduit and the other to said second conduit.

I References Cited UNITED STATES PATENTS 1,848,194 3/1932 McCurrie 128-172 2,099,045 11/1937 Cook 128-191 2,782,108 2/1957 Prentiss 73-26 X 2,916,033 12/1959 Coleman 'l28-2.07 3,006,339 10/1961 Smith 128-491 FOREIGN PATENTS 1,189,767 3/1959 France. 298,016 11/1919 Germany.

23,345 1913 Great Britain. 750,820 6/ 1956 Great Britain.

RICHARD A. GAUDET, Primary Examiner. W. E. KAMM, Assistant Examiner. 

1. APPARATUS FOR SUPER-ATMOSPHERIC OXYGEN THERAPY COMPRISING: (A) A TREATMENT CHAMBER FOR RECEIVING THE PATIENT TO BE TREATED, (B) A DOOR FOR SAID CHAMBER FOR SEALING THE LATTER WITH THE PATIENT THEREIN, (C) A SOURCE OF HIGH PRESSURE OXYGEN, (D) AN INLET TO SAID CHAMBER, (E) AN OUTLET FROM SAID CHAMBER, (F) A CONDUIT CONNECTING SAID SOURCE TO SAID INLET, (G) MEANS FOR CONTROLLING INCREASE OF PRESSURE IN SAID CHAMBER FROM ATMOSPHERIC UP TO THE DESIRED TREATMENT PRESSURE, (H) MEANS FOR PREVENTING SAID TREATMENT PRESSURE EXCEEDING A SET VALUE, (I) MEANS FOR CONTROLLING DECREASE OF PRESSURE IN SAID CHAMBER FROM THE TREATMENT PRESSURE DOWN TO ATMOSPHERIC, 